The objective of this research is to elucidate the sequence of events which occurs when one cell type is accepted or rejected by cells of a different cell type. The differences between normal and cancer cells in this respect will be investigated. Specifically, this specificity of interaction of cells will be investigated by studying the following areas: the specific adhesion of cells from normal and tumor sources to aggregates and fragments of normal and tumor tissue; the inhibitory effect of mouse cancer cells on the aggregation of normal cells; and the effect of inhibitors of a wide range of cell metabolic processes on these specific interactions.